The Doctor is an incredibly complicated character, but when you boil it down to a basic strapline, they're mainly a figure of hope, happiness, and inspiration.
The vast majority of Doctor Who stories involve the Doctor trying to make other people's lives better, and, for the most part, these efforts are a success, with countless individuals, cities, and planets being saved over the years.
But of course, there are two sides to every coin, and the Whoniverse - despite all the good things that happen within it - isn't always sunshine, rainbows, and fluffy little bunny rabbits.
In fact, some characters that the Doctor bumps into have a pretty rough time during their stints on the show, achieving astonishing levels of bad luck that would make even non-superstitious folk raise an eyebrow.
From neglected robot dogs to scorned lovers (and a certain companion who has a tendency to die repeatedly) the Doctor Who universe is full of bad luck - and these unfortunate souls were dealt a significant portion of it. The next time you're having a bad day, just remember: it could be a lot worse.
10. Bill Potts
Overall, Bill Potts had a good time while travelling with the Twelfth Doctor. Sure, being a TARDIS crew-mate means that you'll find yourself in some sticky situations every now and then (and Bill was no exception), but it's not like she was constantly getting friend-zoned like Martha was, or constantly being disrespected like Mickey.
However, her fortunes changed drastically at the end of her arc, where she was subjected to an unbelievable stroke of bad luck that resulted in her grotesque and irreversible transformation into an emotionless robot - also known as a Cyberman.
After being mortally wounded, Bill is transported to the bottom end of a ship that is orbiting a black hole, while the Doctor stays at the top end. At each end of the ship, time moves differently: while recuperating at the bottom, Bill is there for ten years, but for the Doctor, it's only been ten minutes.
At the end of that ten minutes, the Doctor takes the elevator down to the bottom end of the ship, but he's too late: Bill's Cyber-transformation has already been completed.
The Master then comments on how close the Doctor was to rescuing Bill and saving her from this horrific fate, summing up how devastatingly unlucky she really was:
"Ten years you spent up there, chatting. You missed her by two hours."
Basically, if the Doctor had said one or two less words, taken a few less paces, and been just a fraction quicker in getting to that elevator, the time dilation means that he would've reached Bill before she was operated on.
Really takes the phrase "every second counts" to a whole other level, doesn't it?